Vibration absorbing support for loudspeaker voice coil bobbin

ABSTRACT

The suspension wires extending tangentially to the outer periphery of the coil bobbin which is positioned within a cylindrical air gap of the magnetic circuit of a loudspeaker partially defined by an annular magnetic plate forming a portion of that circuit and a cylindrical pole centered within the plate, are fixed at their outer end to the magnetic plate and are fixed at their inner end to the periphery of the bobbin by vibration absorbing members. The vibration absorbing members may comprise silicone rubber blocks having grooved outer surfaces to receive ends of the wires.

PATENIEBAUG 61974 FIG. I

FIG. 3

VIBRATION ABSORBING SUPPORT FOR LOUDSPEAKER VOICE COIL BOBBIN Thisinvention relates to loudspeakers of the type wherein a voice coilbobbin having a voice coil wound about the bobbin periphery is suspendedwithin a cylindrical air gap formed within the magnetic circuit, andmore particularly, where the voice coil bobbin is suspended by aplurality of suspension wires which extend tangentially to the peripheryof the bobbin and are coupled at one end to the bobbin periphery and atthe other end to a stationary element of the magnetic circult.

SUMMARY OF THE INVENTION The present invention provides a loudspeaker inthe form of an improved structure which insures no interference betweenthe inherent vibrations of the suspension wires themselves and thevibration of the voice coil bobbinwhich is driven by an appliedelectrical signal current to the voice coil and in which the loudspeakeris characterized by superior sound reproduction.

In a preferred form, the loudspeaker which includes a cylindrical bobbinhaving a voice coil wound about its periphery and which is suspendedwithin a cylindrical air gap of the loudspeaker magnetic circuit bymeans of a plurality of suspension wires extending in circumferentiallyspaced fashion tangentially to the outer periphery of the bobbin andeach fixed at their inner end to the periphery of the bobbin and attheir outer end to a fixed magnetic member partially forming themagnetic circuit and the air gap, is characterized by a vibrationabsorbing member which fixes the inner end of each wire to the bobbinperiphery. Preferably, the vibration absorbing member comprises aresilient block formed of silicone rubber or the like and is provided onits outer face with a groove which in turn receives the inner end of thewire. The block may be adhesively affixed to the periphery of the bobbinand the wire in turn adhesively affixed to the grooved surface.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view,partially cut away, of a loudspeaker incorporating the wire suspensionmeans of the present invention in one form.

FIG. 2 is an enlarged perspective view of a segment of the loudspeakerillustrated in FIG. 1 showing in greater detail the wire suspensionmeans of the present invention.

FIG. 3 is an enlarged perspective view of a silicone rubber blockemployed as a vibration absorbing member in the suspension system forthe loudspeaker bobbin of FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT In explaining the illustratedembodiment of the present invention in accordance with the drawings,particularly in FIG. I, an annular magnet 1 is provided with a discalyoke 2 secured to one end face of the magnet and is further providedwith an annular plate 3 secured on the opposite end face of the magnet.A columnar pole 4 is secured to yoke 2 so as to define with plate 3, anannular air gap of predetermined width between its peripheral surfaceand the inner periphery of plate 3.

The magnetic circuit is therefore formed by magnet 1, yoke 2, annularplate 3 and columnar pole 4.

About the upper end portion of pole 4 is concentrically disposed acylindrical voice coil bobbin 6, within the air gap, the bobbin 6carrying a voice coil 5 wound about its periphery. The cylindricalassembly consisting of the bobbin 6 and the voice coil 5 has an innerdiameter slightly larger than the diameter of the pole 4 and an outerdiameter slightly smaller than the inner pe- 0 riphery of the plate 3and is disposed within the air gap so as to be able to move freely inthe axial direction, between pole 4 and plate 3. A dome shaped diaphragm7 is attached to the front end of bobbin 6, that is, the end of thebobbin 6 which is remote from yoke 2.

Further, on the upper surface of plate 3, a plurality of terminals 8 (inthe illustrated embodiment, the number is three) are secured thereto.Respective terminals 8 are circumferentially distributed and positionedconcentric with respect to the axis of pole 4 and with a certaincircumferential spacing between respective terminals. One end of thesuspension wires 9 are respectively fixed to the terminals 8.

Each suspension wire is made of a material having high resiliency suchas beryllium-copper alloy. The suspension wires 9 extend in a tangentialdirection relative to the outer periphery of the bobbin 6, inwardly fromterminals 8.

The present invention is directed to fixing the inner ends of thesuspension wires 9 to vibration absorbing members 10 which, in turn, areattached to the periphery of bobbin 6 as shown in greater detail in FIG.2. The vibration absorbing members 10 which are in the form of blocksare preferably made of a suitable viscous resilient material such assilicone rubber as best seen in FIG. 3, each member or block 10 isprovided with a long, and inclined, groove 10a on the face of thesilicone rubber block opposite that contacting the periphery of bobbin6. The groove 10 is so formed and positioned that its supports the innerend of its suspension wire 9 at a preset position, and each suspensionwire 9 is fixed to its vibration absorbing member or block 10 and, inturn, the vibration absorbing member or block 10 is fixed to the bobbin6 by a suitable adhesive. Preferably, the end of the suspension wire 9and the complete mass of the vibration absorbing member or block 10 maybe covered with a layer of suitable vibration absorbing material such assilicone rubber so as to completely embed the end portions of wires 9 inthe vicinity of their point of attachment to the periphery of bobbin 6.

In FIGS. 1 and 2, the mass or layer of silicone rubber which coversblock 10 and the end of wire 9 is illustrated at 11.

In the loudspeaker constructed as above, the bobbin 6 forms onevibrating system and the suspension wires 9 form another vibratingsystem and are coupled to each other in such a state as to be insulatedin relation to vibrations of high frequency. Therefore, especially wherethe vibration is so high in frequency as to cause the suspension wires 9to resonate, vibration components resulting from bobbin 6 being drivenwith an applied electrical signal current, hardly transmits suchvibration to the suspension wires 9 and thus there results littledeterioration in the sound characteristics which normally would resultfrom resonance of the suspension wires 9 as a result of appliedelectrical signals to the coil 5 and it is especially noted toremarkable de- 3 cline in the distortion ratio and high frequency soundrange when the vibration absorbing arrangement of the present inventionis employed.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention What is claimed is:

1. In a loudspeaker including a cylindrical bobbin having a voice coilwound about its periphery and being suspended within a cylindrical airgap of the loudspeaker magnetic circuit by means of a plurality ofsuspension wires extending in circumferentially spaced 3. Theloudspeaker as claimed in claim 2, wherein said blocks are adhesivelyfixed to the periphery of the bobbin and the wires are adhesively fixedto the outer surface of the block.

4. The loudspeaker as claimed in claim 3, wherein the surface of theblocks facing away from the bobbin are grooved, and the inner ends ofthe wires are received within said grooves to preset the bobbin withinsaid air gap.

5; The loudspeaker as'claimed in claim 1, wherein the inner ends of thewires and the vibration absorbing members are embedded in an additionallayer of vibra tion absorbing material. 7

6. The loudspeaker as claimed in claim 4, wherein the inner ends of thewires and the vibration absorbing members are embedded in an additionallayer of vibration absorbing material. V

7. The loudspeaker as claimed in claim 5, wherein said layer ofvibration absorbing material comprises silicone rubber.

8. Th loudspeaker as claimed in claim 6, wherein said block and saidadditional layer of vibration absorbing material comprises siliconerubber.

1. In a loudspeaker including a cylindrical bobbin having a voice coilwound about its periphery and being suspended within a cylindrical airgap of the loudspeaker magnetic circuit by means of a plurality ofsuspension wires extending in circumferentially spaced fashion,tangentially to the outer periphery of the bobbin and each being fixedat its inner end to the bobbin and at its outer end, to a fixed magneticmember partially forming the magnetic circuit, the improvementcomprising: vibration absorbing members respectively fixing the innerends of said suspension wires to said bobbin periphery.
 2. Theloudspeaker as claimed in claim 1, wherein said vibration absorbingmembers comprise blocks of viscous resilient material.
 3. Theloudspeaker as claimed in claim 2, wherein said blocks are adhesivelyfixed to the periphery of the bobbin and the wires are adhesively fixedto the outer surface of the block.
 4. The loudspeaker as claimed inclaim 3, wherein the surface of the blocks facing away from the bobbinare grooved, and the inner ends of the wires are received within saidgrooves to preset the bobbin within said air gap.
 5. The loudspeaker asclaimed in claim 1, wherein the inner ends of the wires and thevibration absorbing members are embedded in an additional layer ofvibration absorbing material.
 6. The loudspeaker as claimed in claim 4,wherein the inner ends of the wires and the vibration absorbing membersare embedded in an additional layer of vibration absorbing material. 7.The loudspeaker as claimed in claim 5, wherein said layer of vibrationabsorbing material comprises silicone rubber.
 8. Th loudspeaker asclaimed in claim 6, wherein said block and said additional layer ofvibration absorbing material comprises silicone rubber.